Optical discs base plate are widely used for digital audio discs, optical video discs, memory discs and magnetic optical discs. In the fabrication of optical discs it is known to place a liquid photocurable composition referred to as the grooving layer between the glass disk and a grooved pattern, referred to as the stamper. The liquid photocurable composition is then irradiated with ultraviolet light thereby forming a hard film. The stamper is then removed from the cured layer. The cured photocurable layer now has replicated the pattern of the stamper.
The photocurable composition used for the grooving layer should possess a number of important characteristics. For example, the compositions should have relatively low viscosity and yet be capable of rapid cure. The cured layer must have low volatility so that the thin film sputtering chambers that are subsequently used in the processing will not become contaminated. Also, the cured film should be able to tolerate high temperatures of up to 150.degree. C. experienced during subsequent thin film sputtering.
Furthermore, the cured layer must maintain good mechanical properties, glass transition (Tg) and modulus at high temperature. Also, the cured composition must be tough and not too brittle. Moreover, the composition should readily separate from the stamper without causing damage to its edge or produce particles upon separation.
Although certain compositions have been suggested for the grooving or primer layer as exemplified by U.S. Pat. No. 4729938 to Tajima, et al., such compositions have not satisfied all of the above desired properties. For example, achieving low viscosity in conjunction with good mechanical properties over a wide range of temperatures has been elusive. Therefore, the prior art compositions could stand improvement.